HVAC communication system

Abstract

A system for communicating across conventional HVAC wiring is provided. The system includes a communication device having a communication module capable of inducing low power, high frequency current signals into a single control wire coupling, for example, a thermostat with a compressor. The communication module includes a power supply module that draws power sufficient to operate the communication module from the existing HVAC wiring, so as to eliminate any need for batteries or external power sources. A second communication module may be coupled to the single control wire. The second communication module operates as a transceiver sending communication signals to, and receiving communication signals from, the communication module. In one embodiment, the communication module is disposed within a building, for example coupled to an electronic thermostat, while the second communication module is disposed outside the building near the compressor. The communication signals are RF modulated signals between 5 and 50 MHz so as to take advantage of and pass across parasitic capacitances found inherent in transformers or other coils disposed within HVAC loads.

1. A HVAC communication system comprising:
 a. a control module; and 
 b. a communication module coupled to the control module; 
 wherein the communication module is configured to communicate through the HVAC communication system by inducing current onto one HVAC control wire, wherein the current has a frequency of between 4 and 50 MHz. 
 
     
     
       2. The HVAC communication system of  claim 1 , wherein the HVAC system operates in conjunction with a HVAC load, further wherein the communication module comprises a communication transformer coupled serially with the control module and the HVAC load. 
     
     
       3. The HVAC communication system of  claim 2 , further comprising:
 a. a thermal sensing element coupled to the control module; 
 b. at least one switch responsive to the thermal sensing element; and 
 c. a low-voltage AC input terminal coupled to the control module; 
 wherein when the at least one switch is closed, the HVAC load is actuated. 
 
     
     
       4. The HVAC communication system of  claim 3 , further comprising a power supply module coupled to the low-voltage AC input terminal, wherein the power supply module receives an amount of power from the low-voltage AC input terminal sufficient to operate the control module and the communication module. 
     
     
       5. The HVAC communication system of  claim 4 , wherein the amount of power is less than a predetermined threshold. 
     
     
       6. The HVAC communication system of  claim 4 , wherein the amount of power is less than 55 milliwatts. 
     
     
       7. The HVAC communication system of  claim 2 , further comprising:
 a. a thermostat coupled to the control module; and 
 b. a HVAC load coupled to the thermostat by way of a single wire running from a coil disposed within the HVAC load to one of the control terminal and the thermostat. 
 
     
     
       8. The HVAC communication system of  claim 7 , further comprising a second control module and a second communication module having a second communication transformer coupled serially with the single wire. 
     
     
       9. The HVAC communication system of  claim 8 , wherein the control module is coupled with the thermostat and is disposed within a building, further wherein the HVAC load and the second communication module are disposed outside the building. 
     
     
       10. The HVAC communication system of  claim 8 , wherein when the communication module is actuated, a communication signal is transmitted across the single wire and is received by the second communication module. 
     
     
       11. The HVAC communication system of  claim 8 , wherein when the second communication module is actuated a second communication signal is transmitted across the single wire and is received by the communication module.